Content Templates
Contents templates are used in ew-vod2cbm to specify the output segmentation and tracks of a channel, but also serve as measures to check if asset entries in a schedule are compatible with the channel. They are further used to generate the manifest and playlist media data properties as well as the media init segments. Therefore, bitrate, resolution, frame rate, video parameter sets, number audio channels are included in the template. The assets do not need to have exactly the same parameter values, but are allowed to vary as described later.
The generally preferred way of creating content templates, is to use
ew-content-template-tool, described below.
JSON Schema for Content Template
The JSON schema of the content template contains core parameters of the
content_info.json schema, and some additional parameters for bitrate matching.
It can contain variants of video, audio, and subtitles as signaled in the media_type field.
The variant array can contain multiple variants
of each type. The table below the schema shows the required parameters for each
media type.
{
"type": "object",
"properties": {
"version": {
"type": "string"
},
"constant_gop_duration_ms": {
"type": "integer"
},
"variants": {
"type": "array",
"items": [
{
"type": "object",
"properties": {
"media_type": {
"type": "string"
},
"subtype": {
"type": "string"
},
"name": {
"type": "string"
},
"bitrate": {
"type": "integer"
},
"width": {
"type": "integer"
},
"height": {
"type": "integer"
},
"sample_aspect_ratio": {
"type": "string"
},
"picture_aspect_ratio": {
"type": "string"
},
"scan_type": {
"type": "string"
},
"sps": {
"type": "string"
},
"pps": {
"type": "string"
},
"codec": {
"type": "string"
},
"frame_rate_fraction": {
"type": "array",
"items": [
{
"type": "integer"
},
{
"type": "integer"
}
]
},
"num_channels": {
"type": "integer"
},
"samplerate": {
"type": "integer"
},
"decoder_config": {
"type": "string"
},
"lang": {
"type": "string"
},
"max_bitrate": {
"type": "integer"
},
"min_bitrate": {
"type": "integer"
}
},
"required": [
"media_type",
"name",
"bitrate",
"codec"
]
}
]
}
}
}
Depending on the media type, there are required fields for a variant. The table below lists all the required fields depending on media type.
| Media type | Required fields |
|---|---|
| Video | media_type subtype name bitrate width height sample_aspect_ratio picture_aspect_ratio scan_type sps pps codec frame_rate_fraction |
| Audio | media_type subtype name bitrate codec num_channels samplerate decoder_config lang |
| Subtitles | media_type name bitrate lang codec |
The fields max_bitrate and min_bitrate are optional for all media types.
Example content template
{
"version": "1.0",
"constant_gop_duration_ms": 1920,
"variants": [
{
"media_type": "video",
"subtype": "h264",
"name": "V1000",
"bitrate": 1000000,
"width": 640,
"height": 360,
"sample_aspect_ratio": "1:1",
"picture_aspect_ratio": "16:9",
"scan_type": "progressive",
"sps": "6764001eacb201405ff2a0",
"pps": "68ebccb22c",
"codec": "avc1.64001E",
"frame_rate_fraction": [
25,
1
],
"max_bitrate": 1500000,
"min_bitrate": 900000
},
{
"media_type": "video",
"subtype": "h264",
"name": "V1500",
"bitrate": 1500000,
"width": 768,
"height": 432,
"sample_aspect_ratio": "1:1",
"picture_aspect_ratio": "16:9",
"scan_type": "progressive",
"sps": "6764001eacb201806f20",
"pps": "68ebccb22c",
"codec": "avc1.64001E",
"frame_rate_fraction": [
25,
1
],
"max_bitrate": 1600000,
"min_bitrate": 1400000
},
{
"media_type": "audio",
"subtype": "aac",
"name": "A128",
"bitrate": 128000,
"codec": "mp4a.40.2",
"num_channels": 2,
"samplerate": 48000,
"decoder_config": "1190",
"lang": "eng"
},
{
"media_type": "subtitles",
"name": "eng_1",
"bitrate": 1000,
"lang": "eng",
"codec": "wvtt"
}
]
}
Creating a Content Template: ew-content-template-tool
A content template does not need to created by hand. It can be created from an ingested asset with:
$ ew-content-template-tool
Usage: bin/ew-content-template-tool [OPTIONS] <content info path> <content_template_path> ...
Options:
-gop-dur-ms int
GOP Duration for template
-version
Get version and build date
For example:
$ ew-content-template-tool -gop-dur-ms 1920 content_info.json content_template.json
Note: The tool makes no verification that the media files actually fulfill the specified GOP duration.
Verifying Assets Before Scheduling: ew-verify-asset
Before attempting to schedule an asset, it can be verified that it matches a specific content template, with:
$ ew-verify-asset
Usage: ew-verify-asset [options]
-i, --input string Asset path
-t, --template string Content template file for the asset(s)
For example:
$ ew-verify-content -i media/matrix-revolutions/ -t content-templates/template_4sGOP_hevc.json
This tool will verify that the asset with regards to video-tracks, codecs etc. Missing subtitle tracks, and (secondary) audio tracks are allowed, and yield warnings.
Non-constant GOP lengths are detected, and rejected, for assets ingested with ew-vodingest. Such irregularities are not detected for assets ingested with the older ew-recorder.